1. Field of the Invention
The present invention relates to an improved process for the preparation of 4-hydroxy-3-(5-methyl-3-isoxazolylcarbamoyl)-2-methyl-2H-1,2-benzothiazine 1,1-dioxide (I).
2. Description of the Prior Art
The preparation of 4-hydroxy-3-(5-methyl-3-isoxazolylcarbamoyl)-2-methyl-2H-1,2-benzothiazine 1,1-dioxide (I) has been described by Zinnes et al. in U.S. Pat. No. 3,822,258. Other novel routes to its preparation have also been described by Sircar et al. in U.S. Pat. No. 2,821,211 and by Lombardino in U.S. Pat. No. 3,853,862. The following intermediates of interest in the process of this invention: ##SPC1##
Have been disclosed in U.S. Pat. Nos. 3,501,466 and 3,591,584 and by Lombardino et al., J. Med. Chem. 14: 173 (1971). These intermediates were used by Zinnes in U.S. Pat. No. 3,822,258 for the preparation of the subject compound (I) and by Lombardino in U.S. Pat. No. 3,591,584 for the preparation of related benzothiazine amides, useful as anti-inflammatory agents.